1. Field of the Invention
This invention relates to turn signals for motor vehicles; and more particularly relates to a novel and improved self-contained turn signal flasher unit incorporating a time delay and audible alarm within a common housing to emit an audible tone within the optimal hearing range of the driver which can be more easily heard in the presence of road noise or by persons with impaired hearing.
2. Statement of the Problem
Turn signal circuits are now provided as original equipment on virtually every type of motor vehicle and operate on essentially the same principle; namely, movement of a lever on a steering column will, through a flasher unit, cause a directional light on the automobile to blink at a predetermined rate so as to signal traffic that a turn is intended and, after completing the turn, the flasher unit is automatically canceled when the steering column returns to its original position. There are occasions when the turn signal unit is activated to indicate an intended turn and the turn is not completed or at least not to a degree sufficient to cancel the flashing signal when the turn is completed, and the driver thereafter fails to manually disengage the flasher unit. Not only is this a source of annoyance to other drivers but can create an unsafe condition in misleading other drivers into believing that a car is turning when in fact the turn signal has been accidentally left on. The audible clicking noise resulting from activation of the blinker circuit has proven to be of little value, since it is a type of sound that is difficult to hear for those with impaired hearing or when extraneous noise is present, such as for example, congested traffic areas or when the radio is playing.
Efforts have been made to overcome this problem by utilization of buzzers or bell tones and, for example, reference is made to U.S. Pat. Nos. 2,958,071 to Siefke and 2,896,190 to Gallaro, et al. Another reference of interest is U.S. Pat. No. 2,210,619 to Farrand for utilizing audible signals which are intended to be activated simultaneously with visual signal lights. Still another approach is disclosed in U.S. Pat. No. 3,315,226 to Fernekes in which an armature will cause a striker arm to engage the outer casing of the unit to warn the operator that the turn signal is in operation. In U.S. Pat. No. 3,964,019 to Wethe, et al., an audible alarm is employed in series with an SCR for use in a turn signal circuit, and a timing circuit is utilized in conjunction with the brake switch in the vehicle so that activation of the alarm is delayed in the event that turning is delayed by traffic or a traffic signal. U.S. Pat. No. 3,806,868 to Portman also discloses plural timing circuits with an audio frequency oscillator for use in conjunction with a standard flasher unit to provide a continuous audio tone or buzzer after a preset delay following activation of the turn signal. U.S. Pat. No. 4,933,665 to Bull, et al., discloses a turn signal non-return indicator which activates an audible alarm. The Bull device apparently requires at least three tap wires for interconnection with the turn signal circuitry of the automobile. Alternatively an adapter is employed between the existing socket and the flasher unit. U.S. Pat. No. 4,754,256 to Fluhr, et al., discloses another type of audible turn signal device housed in a self-contained plug-in module for releasable insertion into an adapter socket in the top of a flasher unit.
3. Solution to the Problem
The systems described suffer from a number of drawbacks, among which are the inability to produce a pure tone audible alarm in the optimal hearing range and which can be easily heard by persons with mild hearing loss notwithstanding the presence of extraneous noise factors. By "pure tone" is meant a single frequency tone in sinusoidal waveform. Moreover, systems of the type described which employ audible alarm circuits must be permanently wired into the motor vehicle and are not available as a part of a unitary, self-contained module that can be plugged directly into the socket provided for a conventional turn signal flasher canister. In this relation, it is highly desirable that the alarm be capable of being directly incorporated into the flasher circuit and be sufficiently compact that it can be combined with the flasher circuit in a common housing or canister without increasing its size for direct replacement of the standard turn signal canister units. These features facilitate upgrading of the turn signal systems of existing vehicles to incorporate this pure-tone safety feature for the relatively low cost of the new flasher unit itself. Replacement requires no mechanical or electrical skill beyond unplugging the existing turn signal canister and inserting the new unitary, self-contained module into the existing socket.